Just a quick question,
My wife has a 2001 A4 quattro 2.8l with no heat. Last week, I flushed the heater core, which seemed to resolve the issue, but only for about a day and a half. Afterwards, the car was producing copious amounts of heat. However, after about 60-90 minutes of driving time, the car was back to producing next to no heat. Also, it was a power flush with a pump forcing hot water in both directions through the core. The coolant coming from the core never had any debris in it whatsoever. My question's are:

Could it be air in the heater core preventing coolant flow?

What temperature should the oil temp gauge read at? If it's not getting high enough, could the thermostat be bad? The temp gauge sits right at 12 o'clock after the car has been running for a while, so I'm hesitant to believe it's that.

I live in central Vt, so we seem temps in the mid teens to lower 20's on average in the winter.

Thanks for your responses.

 

Although I have an A6, there should be similarities. I live in sw MI.

First, I find that my heater does not blow out really hot air ever. I can force it to be a little hotter by adjusting the temperature to HI. However, in general it seems to gradually warm up the cabin (I usually set the temps to 72o) and maintain that temperature. When the cabin reaches the proper temperature, the fan will slow down automatically.

My water temp gauge, when the car is a operating temperature, moves to dead center and stays there regardless of outside temperature. Wait -- in summer 90o weather, when caught in a traffic jam, it moves a needle's width to the right (hotter).

The oil gauge usually rises to ~225o in the summer, and hard acceleration or running at 80-90 causes it to approach 250o, but that is rare. Just this winter I have been watching it, and when it is 0-10s it runs around 200-210o and in the 20-30s it runs 210-225o. This holds true whether I drive it at 60 or 90.